1. Field of the Invention
The present invention relates to a recording method for a phase change optical recording medium, and, in particular, to a recording method for a rewritable DVD medium.
2. Description of the Related Art
Recently, a large size of image data is handled, and, therefore, a recording medium therefor thus having a larger storage capacity is demanded. Further, it is also demanded to record such a large size of image data in the recording medium and reproduce the same therefrom at high speed. A technique of phase change optical recording medium is applied to a CD or DVD rewritable recording medium, and has been wide used since it has characteristics of having a large storage capacity and has a high compatibility with a ROM. Especially., high speed recording/playback has been achieved with CD-ROM or CD-R, and, as a result, a phase change optical recording medium is also demanded to have a performance such that high speed recording/playback can be achieved therewith. Furthermore, it is preferable that a disk which has a performance of high speed recording/playback should also have a capability of recording thereto also with a low-speed disk drive which is originally designed for a disk for a low recording linear velocity. In fact, a CD-R in the market has such a performance, thus covering a wide range of recording linear velocity.
On the other hand, in order to achieve high speed recording, a high-power laser which can provide a higher peak power is needed. However, in general, an optical output of a laser mounted in a low-speed disk drive is lower than the output of a high-speed disk drive. Therefore, it is difficult to achieve recording on a disk designed for a high linear velocity with a low linear velocity and with a lower power in case a phase change optical recording medium is applied.
In case of applying a phase change optical recording medium, a medium configuration is optimized so that recording at a high linear velocity is achieved. However, as a result, an optimum peak power increases even in a case of recording at a low linear velocity same as in a case of recording at a high linear velocity. In order to achieve recording at a lower linear velocity on a recording medium which is designed for recording at a high linear velocity, it is necessary to improve sensitivity. For this purpose, there is a method in which the reflectance of a recording medium is decreased. However, in a case of DVD, in order to provide a compatibility with a DVD-ROM, it is not possible to lower the reflectance more than necessary. In a case of a rewritable DVD, the maximum linear velocity is 2.4 time speed (2.4×) in the market within recent several years, and, there is no backward compatible phase change optical recording medium such that recording can be achieved thereon at a linear velocity higher than the above-mentioned maximum linear velocity, and also, recording can be achieved thereon also with a conventional disk drive designed merely for low linear velocity recording.
In order to satisfy this requirement, it is necessary to find out a recording material and a medium configuration for a phase change optical recording medium on which recording can be achieved with a low power and also having a wide margin of peak power, and to create an optimum recording method therefor. As such a recording method, Japanese Patent No. 2941703 discloses a method for forming a record mark in which a tail pulse bias power application ending time is determined without regard to a recording linear velocity. However, in this method, it may be difficult to obtain satisfactory recording characteristics for a wide range of recording linear velocity.
Japanese laid-open patent application No. 2001-060319 discloses a method in which a peak pulse power application interval and a subsequent multi-pulse peak power application interval are changed according to a recording linear velocity, a bias power application interval is provided at the pulse tail, these intervals are optimized, and, thus, satisfactory recording characteristics can be obtained. However, this method does not include a method applicable for a CAV manner.
Further, Japanese laid-open patent application No. 2001-118245 discloses a method based on the above-mentioned method which is applicable to a CAV (constant angular velocity) manner in which a recording linear velocity changes continuously from a low linear velocity through a high linear velocity as a recording radial position on the disk optical recording medium changes from an inner circumferential part through an outer circumferential part. In this method, a top peak power application starting time is fixed, the peak power application interval is changed, and further a subsequent multi-pulse peak power application interval is changed for each linear velocity in CAV recording. However, in this method, since a recording manner in which both the top pulse starting time and the power application interval are changed is not applied, it may not be possible to precisely control a starting position of a top of a mark actually recorded.
Other than the above, the applicant of the present application proposed by Japanese patent application No. 2002-261281, a method applicable to CAV recording on a recording medium which is compatible in recording/playback with a disk drive with a maximum linear velocity of 2.4 time speed (2.4×).
However, in this method, control of a top peak power application starting time may not be sufficient and thus there may occur a case where a satisfactory performance is not obtained for a certain item in recording characteristics.